In order to increase the efficiency and the performance of gas turbines so as to provide increased power generation, lower emissions and improved specific fuel consumption, turbines are tasked to operate at higher temperatures and under harsher conditions. Such conditions become a challenge for cooling of certain materials.
As operating temperatures have increased, new methods of cooling alloys have been developed. For example, ceramic thermal barrier coatings (TBCs) are applied to the surfaces of components in the stream of the hot effluent gases of combustion to reduce the heat transfer rate and to provide thermal protection to the underlying metal and allow the component to withstand higher temperatures. Also, cooling holes are used to provide film cooling to improve thermal capability or protection. Concurrently, ceramic matrix composites (CMCs) have been developed as substitutes for some alloys. The CMCs provide more desirable temperature and density properties in comparison to some metals; however, they present additional challenges.
A number of techniques have been used in the past to manufacture turbine components having CMCs. For example, SiC/SiC CMCs have been formed from 2-D ceramic fiber plies. However, such materials have inherently low interlaminar properties. In many applications, thermal gradients and mechanical loads that result from operation result in significant local interlaminar stresses.
One known technique of handling interlaminar stresses includes use of ceramic matrix pins/plugs. In that technique, the matrix-only pins/pugs that do not include fibers can be susceptible to fast-fracture and can lack toughness.
Another known technique includes a splay that partially separates a pressure side and a suction side of a turbine blade in the root. In that technique, the load path is not completely separated because the splay is limited to the root and the blade is a solid (not hollow) blade. This results in limitations on reducing, relieving, or eliminating the interlaminar stresses. In addition, such techniques are limited to in-plane stresses and do not include properties associated with transverse features, such as, weaves or tows.
A turbine component, a turbine blade, and a turbine component fabrication process that do not suffer from one or more of the above drawbacks would be desirable in the art.